There has long existed a need for a robust adhesive and method for bonding vulcanized rubber or other cured elastomers to metal and other substrates. In most rubber bonding processes, a traditional rubber-to-substrate adhesive, such as Chemlok® adhesives sold by LORD Corporation, is applied to a metal part, which is then loaded into a mold and unvulcanized rubber or other elastomer is injected into the mold. The rubber filled mold is then heated to co-cure the adhesive during vulcanization of the rubber. This ensures a robust bond between the rubber and metal substrates.
There are, however, applications where co-curing an adhesive with the rubber is impractical or impossible. For example, during tank-lining applications large sheets of elastomer are bonded to the inside of a rail car or other large industrial tank and the inside surface of the large tank or rail car must be heated and pressurized to bond and vulcanize the rubber. This requires the entire tank to be heated and pressurized for a period of time to complete the curing/bonding processes. It would be preferable to cure the elastomer prior to the lining operation, then bond the cured elastomer to the interior of the tank without any externally applied heat or pressure. In other circumstances, post-vulcanization rubber-to-substrate bonding can provide significant cost advantages compared to in-mold bonding of smaller parts. In all of these instances, it is desirable to form a rubber-tearing bond between the vulcanized rubber and a rigid substrate such as metal.
Prior art solutions to post-vulcanization elastomer-to-metal bonding tend to be tailored to specific industry needs. For example, in the tank lining industry where metallic tanks are lined with rubber or other elastomers there is a recognized industry standard. This process involves surface treatment of the elastomer and metal to “roughen” the substrates, then a coat of solvent-based primer and adhesive on the metal, as well as one or two solvent-based adhesive coats on the elastomer side with drying steps in-between each coating. Then the coated substrates are brought into contact and cured sometimes under heat and pressure. This entire process is time consuming and involves the use of solvent-based and halogen and isocyanate containing materials.
It is therefore desirable to provide materials and a method for post-vulcanization bonding of elastomers, such as natural rubber, to another substrate such as the same or different elastomer (either vulcanized or unvulcanized), and non-elastomeric substrates such as steel and engineered polymers.
It is to these perceived needs that the present invention is directed.